Treatments of bis (diphenylphosphino) methylene (dppm) bridged dicobalt complex, Co2 (CO) 6 (μ-Ph2PCH2PPh2), with alkynes, Ph2PC CR (2: R= CMe3; 3: R= SiMe3), at 60° C in THF for 6 h gave alkyne-bridged complexes [(μ-Ph2PCH2PPh2) Co2 (CO) 4][(μ-Ph2PC CR)](4: R= CMe3; 5: R= SiMe3). Further reactions of 4 and 5 with Co2 (CO) 8 at 80° C in toluene for 3 h resulted in the formations of unexpected tetra-cobalt clusters,[(μ- ...